Arms Index (TRIN)

The Arms Short-Term Trading Index, commonly known as TRIN, shows the relationship between
stocks that are advancing/declining in price and the volume associated with these stocks.
It is calculated by dividing the Advance/Decline Ratio by the Up/Down Ratio.

The Arms Index is a short-term trading tool. The goal of the indicator is to determine if
volume is flowing into advancing or declining stocks, and by what magnitude. The Arms Index
was first published by Richard W. Arms, Jr. in 1967. For a more complete explanation of the
Arms Index, see Robert Colby and Thomas Meyers, The Encyclopedia of Technical Market Indicators (New York: Irwin, 1988).

Typically, the Arms Index is interpreted as "bullish" when it is below 1.0 and "bearish" when it is above 1.0.